Hi
I have had this problem a few times and never really got to the bottom of it.
The dishwasher is draining very slowly and water is left in the base.
I have replaced the air chamber (448903) as it was gunked up in the top, but its still draining very slowly.
The strange thing is that if you take the drainage section off the air chamber it drains out into a bucket in about 5 seconds but as soon as I connect the new air chamber the drainage virtually stops, have also put on a new drainage hose.
Has anyone else come across this problem?